1、May 2014DEUTSCHE NORMNormenausschuss Materialprfung (NMP) im DINDIN-SprachendienstEnglish price group 20No part of this translation may be reproduced without prior permission ofDIN Deutsches Institut fr Normung e. V., Berlin. Beuth Verlag GmbH, 10772 Berlin, Germany,has the exclusive right of sale f
2、or German Standards (DIN-Normen).ICS 71.040.40!%1d7“2146520www.din.deDDIN 51898-1Gas analysis Absolute volumetric method for dynamic preparation of calibrationgases Part 1: Preparation from pure gases, with CD-ROM,English translation of DIN 51898-1:2014-05Gasanalyse Absolutes volumetrisches Verfahre
3、n zur dynamischen Herstellung von Kalibriergasen Teil 1: Herstellung aus reinen Gasen, mit CD-ROM,Englische bersetzung von DIN 51898-1:2014-05Analyse des gaz Mthode absolue volumtrique pour la prparation dynamique de mlanges de gaz pourtalonnage Partie 1: Prparation base de gaz pures, avec CD-ROM,Tr
4、aduction anglaise de DIN 51898-1:2014-05www.beuth.deDocument comprises 41 pages11.14 DIN 51898-1:2014-05 2 A comma is used as the decimal marker. Content Page Foreword . 3 Introduction 4 1 Scope . 5 2 Normative references . 5 3 Terms and definitions 6 4 Principle . 6 5 Preparation of calibration gas
5、es . 8 6 Influencing factors 11 6.1 Influencing factors and effects 11 6.2 Supplementary information . 15 7 Calculation of composition 16 7.1 Symbols and abbreviations . 16 7.2 Rough estimates . 17 7.3 Calculation of component contents 17 7.3.1 General . 17 7.3.2 Calculation of discharged gas volume
6、s . 18 7.3.3 Calculation of compression factors 18 7.3.4 Calculation of mole fractions 19 7.3.5 Calculation of volume fractions 19 8 Estimation of uncertainty . 20 8.1 General . 20 8.2 Determination of input uncertainties 20 8.3 Uncertainty of the mole fractions 23 8.4 Uncertainty of the volume frac
7、tions . 24 9 Methods for the verification of a calculated composition 24 9.1 General . 24 9.2 Comparison measurements using traceable gas mixtures . 24 9.3 Comparison measurements using gas density gauges (sinker densimeters) . 25 9.4 Symmetry check of the gas mixing pump 25 10 Test report . 25 Anne
8、x A (informative) Validation and verification 26 A.1 Requirements for validation 26 A.2 Verification of linearity . 26 Annex B (informative) Realized applications 28 Annex C (informative) Example calculations 29 Annex D (informative) Computer program 40 Bibliography . 41 DIN 51898-1:2014-05 3 Forewo
9、rd This document has been prepared by Working Committee NA 062-05-73 AA Gasanalyse und Gasbeschaffenheit of the Normenausschuss Materialprfung (Materials Testing Standards Committee, NMP). Attention is drawn to the possibility that some of the elements of this document may be the subject of patent r
10、ights. DIN shall not be held responsible for identifying any or all such patent rights. In order to facilitate the use of this document the common abbreviation GUM, for Guide to the expression of uncertainty in measurement, is used throughout. The normative references include the German translation
11、DIN V ENV 13005. DIN 51898 Gas analysis Absolute volumetric method for dynamic preparation of calibration gases consists of the following parts: Part 1: Preparation from pure gases Part 2: Preparation from gas mixtures (in preparation) Part 3: Systems with one single piston pump (in preparation) DIN
12、 51898-1:2014-05 4 Introduction Calibration gases with direct traceability to the International System of Units (fr: Systme International dUnits, SI) are of great interest to a large user community and of considerable commercial relevance. Starting from dimensional calibration of the piston pumps in
13、 the SI base unit of length, a mathematical model is presented which serves as a basis for calculating the composition of the calibration gases as well as for estimating the associated uncertainty. Calibration gases prepared according to the absolute volumetric method using piston pumps, as specifie
14、d in this standard, conform to the requirements of direct traceability to the SI. The gas-forwarding geometric volumes of the individual piston pumps are completely determined by their cylinder diameter, piston stroke height and the number of piston strokes. DIN 51898-1 operates on the assumption th
15、at the parent gases are pure gases. DIN 51898-21)also covers the case of gas mixtures as parent gases. The commercially available gas mixing pumps are suitable for the dynamic preparation of two- and multi-component gas mixtures. In contrast with other methods for dynamic gas mixture preparation, th
16、e gas flow forwarded by the individual piston pumps is not calibrated by comparison measurements. The composition of the calibration gases is calculated using the specified mathematical model, where departures from the ideal gas law are accounted for by means of the calculation methods and gas data
17、(pressure virial coefficients) given in DIN EN ISO 14912. Composition is preferably expressed in mole fractions, alternatively also in volume fractions. NOTE As an advantage over volume fractions, mole fractions are independent of pressure and temperature, and they are easily converted into other qu
18、antities of composition (e.g. mass concentrations) as required, using DIN EN ISO 14912. For a defined range, calculated composition can be verified using the engaged mixing pump. The respective procedure is described in the standard. Validation at the highest metrological level is exemplified for ga
19、s mixtures with composition ranges extending over several decades. Minimum requirements and minimum scope of procedures for validating the performance of gas mixing pumps are specified. Provided that rigorous and comprehensive quality assurance and quality control measures are taken in gas mixture p
20、reparation and performance validation, this method has the potential to generate calibration gases of highest accuracy within the validated composition range. 1) In preparation.DIN 51898-1:2014-05 5 1 Scope This document specifies an absolute volumetric method for dynamic preparation of calibration
21、gases consisting of two or several components from pure gases, using commercially available gas mixing pumps with at least two piston pumps driven at defined stroke ratios. Peripheral devices for gas feed and homogenization are also commercially available and constitute a functional unit with the ga
22、s mixing pump. Gas mixing pumps with several piston pumps are suitable for preparing multi-component gas mixtures, where the range of component proportions is determined by the ratio of the geometric stroke volumes of the piston pumps concerned. The geometric stroke volume is equated with the gas vo
23、lume forwarded by the respective piston pump. The prerequisite condition for this process is as follows: when operating the pump at admissible stroke numbers, the conveying factor shall not deviate significantly in comparison to the specified uncertainty from 1. DIN 51898-1 covers the preparation of
24、 calibration gases from commercially available pure gases (post-purified where appropriate), where the effects of impurities of the parent gases on the composition of calibration gases are accounted for in the estimation of uncertainty. Dry air is treated as a pure gas with the composition specified
25、 in DIN EN ISO 14912 and the property data given there. The method affords single-stage dilutions up to 1:1 000 in discrete steps. With optimum configuration and handling, the achievable relative expanded uncertainty of composition (k = 2, confidence level 95 %) amounts to 0,1 % (see 8.3 and 8.4 for
26、 calculation and Annex C for examples). Lower concentrations can be obtained using multi-stage dilution or pre-mixtures (see DIN 51898-21). The range of currently available volume flow rates of calibration gas mixtures goes from 5 l/h to 500 l/h. 2 Normative references The following referenced docum
27、ents, in whole or in part, are normatively referenced in this document and are indispensable for its application. For dated references, only the edition cited applies. For undated references, the latest edition of the referenced document (including any amendments) applies. DIN V ENV 130052), Guide t
28、o the expression of uncertainty in measurement DIN EN ISO 14912, Gas analysis Conversion of gas mixture composition data 2) Identical with GUM.DIN 51898-1:2014-05 6 3 Terms and definitions For the purposes of this document the following terms and definitions apply. 3.1 reference conditions reference
29、 values of the pressure and the temperature of the calibration gas for specifying the composition in volume fractions 3.2 nominal stroke number highest selectable number of strokes of a piston pump 3.3 stroke number product of the preset reduction gear ratio of the switch gear and the nominal stroke
30、 number of a piston pump 3.4 reduction gear ratio quotient of the number of strokes and the nominal stroke number of a piston pump, adjustable in discrete steps by the switch gear 3.5 stroke volume geometric discharge volume per stroke of a piston pump, calculated from cylinder diameter and stroke h
31、eight of the piston 3.6 verification confirmation of the calculated composition of a calibration gas in a given application range through investigations and provision of objective evidence that specified requirements have been fulfilled 3.7 validation confirmation of the preparation method through i
32、nvestigations and provision of objective evidence that the requirements for a specified designated range of calibration gases have been fulfilled 3.8 portion defined amount of a gas whose magnitude can be expressed as amount of substance, mass or volume (at specified conditions of pressure and tempe
33、rature) 4 Principle Dynamic preparation of calibration gases with accurately defined composition is carried out using gas mixing pumps whose centrepiece consists of two or more piston pumps pneumatically separated from each other (see Figures 1, 2 and 3). The piston pumps are driven by a single comm
34、on motor via separate gear trains and switch gears. The ratio of the stroke numbers of the individual pumps to one another is clearly defined by the preset reduction gear ratios. The geometric stroke volumes of the piston pumps are clearly determined by the diameter of the cylinder, the stroke heigh
35、t of the pistons and the respective stroke number. For the calculation of the mole fraction and the volume fraction, the quantities of state of temperature and pressure relating to the gases inside the piston pumps shall be determined and accounted for by the equation of state for gases. DIN 51898-1
36、:2014-05 7 The separately forwarded gas portions are steadily merged and homogenized, thus yielding the requested gas mixture. Since the geometric stroke volumes are constant, different gas compositions are generated by variation of the stroke numbers. On the basis of the preparation principle and t
37、he mathematical model given in this standard, the composition of the calibration gases can be directly calculated in mole fractions and volume fractions. Conversion into other quantities of composition can be performed according to the specifications of DIN EN ISO 14912. Figure 1 Piston pump with tr
38、aceable quantities cylinder diameter d, stroke height h and stroke number N Key 1 Ascending piston, gas intake 2 Piston at top dead centre, switching of the cylinder 3 Descending piston, gas forwarding 4 Piston at bottom dead centre, switching of the cylinder Figure 2 Functional steps of the piston
39、pump DIN 51898-1:2014-05 8 Key 1 Gas 1 2 Gas 2 3 Drive motor 4 Gas 1 + Gas 2 Figure 3 Principle of a gas mixing pump with two piston pumps 5 Preparation of calibration gases The parent gases shall be fed into the piston pumps at slight excess of atmospheric pressure and at constant temperature (pref
40、erably room temperature). The use of bubblers (see Figure 4a) at the gas inlets has been proven to provide appropriate control of excess pressure for prohibiting intake of leak air. The requirement of gas intake at atmospheric pressure can be met by an appropriate configuration of bubblers in the by
41、pass and the correct level of the sealing liquid in the bubblers. The use of finely adjustable needle valves or diaphragm pressure reducing valves is recommended to reduce gas consumption. Before being used, gases taken from compressed gas cylinders shall be decompressed to atmospheric pressure usin
42、g appropriate single-stage or double-stage pressure reducers. By means of the reduction gear ratios the gas streams forwarded by the piston pumps are adjusted to yield the target composition of the calibration gas. After leaving the piston pumps, the gas streams are merged and subsequently conducted
43、 through one or more mixing vessels for homogenization. The homogenization facility (e.g. mixing vessels, see figure 4b) shall be adapted to varied discharge volumes and dilution levels. Homogeneity of gas mixtures shall be demonstrated within the framework of validation, i.e. the efficiency of the
44、mixing vessels shall be verified by appropriate methods for the various gas mixtures concerned. When large quantities of gas are taken from compressed gas cylinders, attention shall be paid to the Joule-Thomson effect (potential cooling of withdrawn gas by decompression or by vaporization of liquefi
45、ed gas). Figure 5 shows an example of a system for dynamic preparation of calibration gases according to the absolute volumetric method. If required, thermostatization of the piston pumps and reheating of the parent gases can be provided (as shown in Figure 6). NOTE 1 Thermostatization of the parent
46、 gases and the piston pumps generally results in a reduction of the overall uncertainty. At the outlet of the overall system the calibration gas is provided at near atmospheric pressure. The flow resistance of mixing vessels, pulsation dampers and gas transfer lines shall be maintained at negligibly
47、 low levels. If higher pressure is required, appropriate measures shall be taken separately. DIN 51898-1:2014-05 9 NOTE 2 Due to the principle of preparation pulsations of gas flow can occur at the system outlet. These pulsations can be reduced by appropriate technical means (e.g. dampers or by-pass
48、es). Before starting the preparation of calibration gases, the overall system shall be checked for leak integrity and contamination of gas lanes. WARNING The parent gases are not permitted to react with each other. If there is a possibility of formation of hazardous gas mixtures, appropriate prevent
49、ive and safety precautions shall be taken. Safe discharge of toxic or flammable gases shall be ensured by the user. If merging of parent gases can generate flammable or explosive mixtures, contact with ignition sources shall be avoided, and applicable safety regulations shall be observed. WARNING When changing the target proportions of the parent gases, due consideration shall be given to the fact that during the adjustment phase short term concentration peaks can
